<html xmlns="http://www.w3.org/1999/xhtml">
    <body>
        <table id="table">
        <caption id="c1">PASS: Text in caption 1</caption>
        <caption id="c2" style="opacity: 0.5">PASS: Text in caption 2</caption>
        <caption id="c3" style="opacity: 0.2">PASS: Text in caption 3</caption>
        <caption id="c4" style="opacity: 0">PASS: Text in caption 4</caption>
        </table>
        <script>
           var caption = document.createElement('caption');
           caption.appendChild(document.createTextNode('PASS: Dynamically added caption'));

           var table = document.getElementById('table');
           var c1 = document.getElementById('c1');
           table.insertBefore(caption, c1);
           document.body.offsetTop;
        </script>
    </body>
</html>